The present invention relates to a poultry leg boning apparatus for removing meat from the poultry legs.
When the meat is manually removed from the poultry leg, the boning work is carried out with a knife by means of the following steps:
(1) cutting the meat of the leg along the upper and lower leg bones;
(2) cutting the knee joint so as to separate the upper leg bone from the lower leg bone;
(3) pulling up the upper leg bone at the lower end thereof or the knee joint and plucking off the upper leg bone from the leg meat;
(4) peeling the meat off the leg along the lower leg bone toward the knee joint so as to make the meat connected only to the knee joint by meat-to-bone connecting tendon tissues; and
(5) cutting the meat-to-bone connecting tendon tissues so as to remove the lower leg bone from the leg meat.
The above steps of the manual boning require skill and physical stamina so that it has been desirable to automate them. Especially in the step (1), there has been the problem that, if a force biasing the knife against the bones is too large, the knife chips the bones and the chips of the bones are left on the meat, which decreases the economic value of the meat. Or, if the force biasing the knife against the bones is too small, the knife comes to be detached from the bones and a certain amount of meat is left on the bones, which decreases the yield of the meat removed from the leg. In the step (5), there has been the problem that, it is hard to bias the knife against the knee joint stably because the knee joint is round and the meat-to-bone connecting tendon tissues are hard, this results in a hazard to the operator or may decrease the commercial value of the meat because of the rough cut surface.
Various types of machines and methods for removing the meat from the poultry leg have been proposed. For example, U.S. Pat. No. 2,897,536 to Bergstrom et al, dated Aug. 4, 1959 discloses a machine wherein the leg is passed through a space between a pair of rotating rollers so that the meat is removed from the leg. U.S. Pat. No. 3,261,054 to Kaplan et al, dated Jul. 19, 1966 discloses a machine wherein the leg is passed through a space between a pair of stripper bars so that the meat is removed from the leg. U.S. Pat. No. 3,965,535 to Kaplan et al, dated Jun. 29, 1976 discloses a machine wherein the leg is passed through a space between a pair of discs rotating with their closely spaced peripheral stripping edges in opposition so that the meat is removed from the leg. U.S. Pat. No. 3,348,261 to Segur dated Oct. 24, 1967 discloses a method wherein the meat of the leg is sliced along at least one side of the leg bone, and thereafter the meat is plowed in opposite directions along the upper leg bone and the lower leg bone toward the knee joint. By means of the above machines and methods, the meat of the leg is forced along the leg bone thereby being removed therefrom. Thus, because of excessive deformation during the boning process, the meat, especially the meat of the upper leg portion, is liable to be damaged more seriously compared with the manually processed meat. Japanese Patent Publication No. 60-23810 dated Jun. 10, 1985 discloses a boning machine having a rotating annular cutter belt. By the machine, the meat between the going run of the cutter belt and the returning run of the cutter belt is left on the leg bone, so that the yield rate of the meat removed from the leg is lower than that by the manual separation.